Congestive heart failure (CHF) is a condition in which blood circulation provided by the heart is impaired. CHF is a common, disabling, and costly condition. CHF can be treated by drug therapy and, sometimes, by implantable cardiac function management devices, such as for providing cardiac resynchronization therapy (CRT). A patient's chronic stable heart failure may abruptly decompensate, requiring hospitalization. Therefore, monitoring a patient's cardiac status, such as for CHF, can help avoid such acute decompensation and hospitalization.